The invention relates to an apparatus for pressing a book casing or a slip-fold against an adhesive-covered back and the adjacent side flanks of a book block, which is transported while clamped into a circulating clamp of a perfect binder with the back projecting downward. Such an apparatus includes a device for respectively pressing the casing against the adhesive-covered back, and a device for pressing the casing against the side flanks, wherein these devices are driven with the synchronous timing of the clamps for transporting the book blocks.
In a perfect binder, a casing or slip-fold is attached with the aid of adhesive to the back of a book block, composed of loosely gathered sheets. In the process, the back of the book block is first treated to ensure a good connection with the adhesive, the adhesive is then applied to the treated back and/or the casing or a slip-fold and the two parts are joined and pressed against each other. Perfect binders are provided with a plurality of clamps that are attached uniformly spaced apart to a traction device and circulate along an endless path. The book blocks are clamped into these clamps during the complete binding process, such that the backs of the book blocks project downward from the clamps and the side areas adjacent to the back, called the flanks, are freely accessible. Once the unbound book blocks have been transferred to these clamps, they are conveyed past the processing stations arranged along the circular path and are treated at these stations while they are conveyed past.
The shape and the strength of the book back are important quality features for the binding of a book and are determined in particular also by the function of pressing on the casing or the slip-fold. Known apparatuses for pressing a casing or slip-fold against the back of a book block include a flat back pressing device for pressing the casing against the book back, as well as a flank pressing device, for pressing the casing in the side area adjacent to the book back against the book block by using pressure bars. The shape of the back can be influenced by the chronological sequences between pressing the casing against the back and against the flanks. For example, the backs of books generally have a tendency to be rounded if the flank pressing device reaches the end position on the inside before the back pressing device reaches the upper final position. On the other hand, if the back pressing device reaches its upper end position before the flank pressing device reaches its inner end position, the book backs have a tendency to be angular. The stroke of the flank pressing device must therefore be adjusted to the product against which it is pressed. A larger stroke is generally required for processing the casings than for processing the slip-folds, which can be adjusted by replacing control cams or through a manual adjustment of the drive coupling system.
German patent document DE 102 27 950 A1 discloses an apparatus for pressing on a casing, which is provided with a control cam, a pivoting lever, and a cam roller for jointly controlling the operation of the flank pressure bars. By moving the lever to different positions, the stroke of the flank pressure bars can be adjusted. This solution has the disadvantage that the adjustments can mutually influence each other and that furthermore the phase position of the flank-pressing device, relative to the back pressing device, cannot be changed.
It is also known to operate the flank pressure bars directly with the aid of assigned control cams or crank gears, wherein at least the inside end position of a flank pressure bar is embodied to be adjustable for being adapting to the book thickness. The respective control cams or cranks must be replaced for changing the stroke of the flank pressure bar. A high time expenditure is required for replacing parts, which is a disadvantage of this solution.
During the pressing operation, there should be no or only an insignificant relative speed between the pressing operation and the book block in the longitudinal direction of the book back.
On the whole, the apparatus is operated either with the aid of a mechanical connection to the drive for the perfect binder, or with the aid of an individual electric drive, which follows the drive for the perfect binder.
Known solutions using only a single drive for the complete apparatus for pressing on a book casing or slip-fold have the disadvantage that the excess load safety for the single drive lacks response sensitivity because the drive must be adjusted such that it can securely transmit the maximum operating forces without responding. As a result, a response to an excess load of elements with a smaller force requirement is not possible. Known apparatuses furthermore have the disadvantage that mechanical drive elements such as cranks or control cams depend on the division between the clamps.